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        <h1>
          <span class="m-breadcrumb"><a href="namespacetf.html">tf</a>::<wbr/></span>ObserverInterface <span class="m-thin">class</span>
        </h1>
        <p>class to derive an executor observer</p>
        <nav class="m-block m-default">
          <h3>Contents</h3>
          <ul>
            <li>
              Reference
              <ul>
                <li><a href="#derived-classes">Derived classes</a></li>
                <li><a href="#typeless-methods">Constructors, destructors, conversion operators</a></li>
                <li><a href="#pub-methods">Public functions</a></li>
              </ul>
            </li>
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<p>The <a href="classtf_1_1ObserverInterface.html" class="m-doc">tf::<wbr />ObserverInterface</a> class allows users to define custom methods to monitor the behaviors of an executor. This is particularly useful when you want to inspect the performance of an executor and visualize when each thread participates in the execution of a task. To prevent users from direct access to the internal threads and tasks, <a href="classtf_1_1ObserverInterface.html" class="m-doc">tf::<wbr />ObserverInterface</a> provides immutable wrappers, <a href="classtf_1_1WorkerView.html" class="m-doc">tf::<wbr />WorkerView</a> and <a href="classtf_1_1TaskView.html" class="m-doc">tf::<wbr />TaskView</a>, over workers and tasks.</p><p>Please refer to <a href="classtf_1_1WorkerView.html" class="m-doc">tf::<wbr />WorkerView</a> and <a href="classtf_1_1TaskView.html" class="m-doc">tf::<wbr />TaskView</a> for details.</p><p>Example usage:</p><pre class="m-code"><span class="k">struct</span><span class="w"> </span><span class="nc">MyObserver</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="k">public</span><span class="w"> </span><span class="n">tf</span><span class="o">::</span><span class="n">ObserverInterface</span><span class="w"> </span><span class="p">{</span><span class="w"></span>

<span class="w">  </span><span class="n">MyObserver</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&amp;</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">    </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot;constructing observer &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="sc">&#39;\n&#39;</span><span class="p">;</span><span class="w"></span>
<span class="w">  </span><span class="p">}</span><span class="w"></span>

<span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="n">set_up</span><span class="p">(</span><span class="kt">size_t</span><span class="w"> </span><span class="n">num_workers</span><span class="p">)</span><span class="w"> </span><span class="k">override</span><span class="w"> </span><span class="k">final</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">    </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot;setting up observer with &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">num_workers</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot; workers</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">;</span><span class="w"></span>
<span class="w">  </span><span class="p">}</span><span class="w"></span>

<span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="n">on_entry</span><span class="p">(</span><span class="n">WorkerView</span><span class="w"> </span><span class="n">w</span><span class="p">,</span><span class="w"> </span><span class="n">tf</span><span class="o">::</span><span class="n">TaskView</span><span class="w"> </span><span class="n">tv</span><span class="p">)</span><span class="w"> </span><span class="k">override</span><span class="w"> </span><span class="k">final</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">    </span><span class="n">std</span><span class="o">::</span><span class="n">ostringstream</span><span class="w"> </span><span class="n">oss</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">oss</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot;worker &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">w</span><span class="p">.</span><span class="n">id</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot; ready to run &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">tv</span><span class="p">.</span><span class="n">name</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="sc">&#39;\n&#39;</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">oss</span><span class="p">.</span><span class="n">str</span><span class="p">();</span><span class="w"></span>
<span class="w">  </span><span class="p">}</span><span class="w"></span>

<span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="n">on_exit</span><span class="p">(</span><span class="n">WorkerView</span><span class="w"> </span><span class="n">w</span><span class="p">,</span><span class="w"> </span><span class="n">tf</span><span class="o">::</span><span class="n">TaskView</span><span class="w"> </span><span class="n">tv</span><span class="p">)</span><span class="w"> </span><span class="k">override</span><span class="w"> </span><span class="k">final</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">    </span><span class="n">std</span><span class="o">::</span><span class="n">ostringstream</span><span class="w"> </span><span class="n">oss</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">oss</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot;worker &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">w</span><span class="p">.</span><span class="n">id</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot; finished running &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">tv</span><span class="p">.</span><span class="n">name</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="sc">&#39;\n&#39;</span><span class="p">;</span><span class="w"></span>
<span class="w">    </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">oss</span><span class="p">.</span><span class="n">str</span><span class="p">();</span><span class="w"></span>
<span class="w">  </span><span class="p">}</span><span class="w"></span>
<span class="p">};</span><span class="w"></span>
<span class="w">  </span>
<span class="n">tf</span><span class="o">::</span><span class="n">Taskflow</span><span class="w"> </span><span class="n">taskflow</span><span class="p">;</span><span class="w"></span>
<span class="n">tf</span><span class="o">::</span><span class="n">Executor</span><span class="w"> </span><span class="n">executor</span><span class="p">;</span><span class="w"></span>

<span class="c1">// insert tasks into taskflow</span>
<span class="c1">// ...</span>
<span class="w">  </span>
<span class="c1">// create a custom observer</span>
<span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">MyObserver</span><span class="o">&gt;</span><span class="w"> </span><span class="n">observer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">executor</span><span class="p">.</span><span class="n">make_observer</span><span class="o">&lt;</span><span class="n">MyObserver</span><span class="o">&gt;</span><span class="p">(</span><span class="s">&quot;MyObserver&quot;</span><span class="p">);</span><span class="w"></span>

<span class="c1">// run the taskflow</span>
<span class="n">executor</span><span class="p">.</span><span class="n">run</span><span class="p">(</span><span class="n">taskflow</span><span class="p">).</span><span class="n">wait</span><span class="p">();</span><span class="w"></span></pre>
        <section id="derived-classes">
          <h2><a href="#derived-classes">Derived classes</a></h2>
          <dl class="m-doc">
            <dt>
              class <a href="classtf_1_1ChromeObserver.html" class="m-doc">ChromeObserver</a>
            </dt>
            <dd>class to create an observer based on Chrome tracing format</dd>
            <dt>
              class <a href="classtf_1_1TFProfObserver.html" class="m-doc">TFProfObserver</a>
            </dt>
            <dd>class to create an observer based on the built-in taskflow profiler format</dd>
          </dl>
        </section>
        <section id="typeless-methods">
          <h2><a href="#typeless-methods">Constructors, destructors, conversion operators</a></h2>
          <dl class="m-doc">
            <dt id="adfd71c3af3ae2ea4f41eed26c1b6f604">
              <span class="m-doc-wrap-bumper"><a href="#adfd71c3af3ae2ea4f41eed26c1b6f604" class="m-doc-self">~ObserverInterface</a>(</span><span class="m-doc-wrap">) <span class="m-label m-flat m-info">defaulted</span> <span class="m-label m-flat m-warning">virtual</span></span>
            </dt>
            <dd>virtual destructor</dd>
          </dl>
        </section>
        <section id="pub-methods">
          <h2><a href="#pub-methods">Public functions</a></h2>
          <dl class="m-doc">
            <dt>
              <span class="m-doc-wrap-bumper">void <a href="#a41e6e62f12bf9d9dc4fa74632f6825d9" class="m-doc">set_up</a>(</span><span class="m-doc-wrap">size_t num_workers) <span class="m-label m-flat m-warning">pure virtual</span></span>
            </dt>
            <dd>constructor-like method to call when the executor observer is fully created</dd>
            <dt>
              <span class="m-doc-wrap-bumper">void <a href="#a8225fcacb03089677a1efc4b16b734cc" class="m-doc">on_entry</a>(</span><span class="m-doc-wrap"><a href="classtf_1_1WorkerView.html" class="m-doc">WorkerView</a> wv,
              <a href="classtf_1_1TaskView.html" class="m-doc">TaskView</a> task_view) <span class="m-label m-flat m-warning">pure virtual</span></span>
            </dt>
            <dd>method to call before a worker thread executes a closure</dd>
            <dt>
              <span class="m-doc-wrap-bumper">void <a href="#aa22f5378154653f08d9a58326bda4754" class="m-doc">on_exit</a>(</span><span class="m-doc-wrap"><a href="classtf_1_1WorkerView.html" class="m-doc">WorkerView</a> wv,
              <a href="classtf_1_1TaskView.html" class="m-doc">TaskView</a> task_view) <span class="m-label m-flat m-warning">pure virtual</span></span>
            </dt>
            <dd>method to call after a worker thread executed a closure</dd>
          </dl>
        </section>
        <section>
          <h2>Function documentation</h2>
          <section class="m-doc-details" id="a41e6e62f12bf9d9dc4fa74632f6825d9"><div>
            <h3>
              <span class="m-doc-wrap-bumper">void tf::<wbr />ObserverInterface::<wbr /></span><span class="m-doc-wrap"><span class="m-doc-wrap-bumper"><a href="#a41e6e62f12bf9d9dc4fa74632f6825d9" class="m-doc-self">set_up</a>(</span><span class="m-doc-wrap">size_t num_workers) <span class="m-label m-warning">pure virtual</span></span></span>
            </h3>
            <p>constructor-like method to call when the executor observer is fully created</p>
            <table class="m-table m-fullwidth m-flat">
              <thead>
                <tr><th colspan="2">Parameters</th></tr>
              </thead>
              <tbody>
                <tr>
                  <td style="width: 1%">num_workers</td>
                  <td>the number of the worker threads in the executor</td>
                </tr>
              </tbody>
            </table>
          </div></section>
          <section class="m-doc-details" id="a8225fcacb03089677a1efc4b16b734cc"><div>
            <h3>
              <span class="m-doc-wrap-bumper">void tf::<wbr />ObserverInterface::<wbr /></span><span class="m-doc-wrap"><span class="m-doc-wrap-bumper"><a href="#a8225fcacb03089677a1efc4b16b734cc" class="m-doc-self">on_entry</a>(</span><span class="m-doc-wrap"><a href="classtf_1_1WorkerView.html" class="m-doc">WorkerView</a> wv,
              <a href="classtf_1_1TaskView.html" class="m-doc">TaskView</a> task_view) <span class="m-label m-warning">pure virtual</span></span></span>
            </h3>
            <p>method to call before a worker thread executes a closure</p>
            <table class="m-table m-fullwidth m-flat">
              <thead>
                <tr><th colspan="2">Parameters</th></tr>
              </thead>
              <tbody>
                <tr>
                  <td style="width: 1%">wv</td>
                  <td>an immutable view of this worker thread</td>
                </tr>
                <tr>
                  <td>task_view</td>
                  <td>a constant wrapper object to the task</td>
                </tr>
              </tbody>
            </table>
          </div></section>
          <section class="m-doc-details" id="aa22f5378154653f08d9a58326bda4754"><div>
            <h3>
              <span class="m-doc-wrap-bumper">void tf::<wbr />ObserverInterface::<wbr /></span><span class="m-doc-wrap"><span class="m-doc-wrap-bumper"><a href="#aa22f5378154653f08d9a58326bda4754" class="m-doc-self">on_exit</a>(</span><span class="m-doc-wrap"><a href="classtf_1_1WorkerView.html" class="m-doc">WorkerView</a> wv,
              <a href="classtf_1_1TaskView.html" class="m-doc">TaskView</a> task_view) <span class="m-label m-warning">pure virtual</span></span></span>
            </h3>
            <p>method to call after a worker thread executed a closure</p>
            <table class="m-table m-fullwidth m-flat">
              <thead>
                <tr><th colspan="2">Parameters</th></tr>
              </thead>
              <tbody>
                <tr>
                  <td style="width: 1%">wv</td>
                  <td>an immutable view of this worker thread</td>
                </tr>
                <tr>
                  <td>task_view</td>
                  <td>a constant wrapper object to the task</td>
                </tr>
              </tbody>
            </table>
          </div></section>
        </section>
      </div>
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